Among the shortcomings of the A* algorithm, for example, there are many search nodes in path planning, and the calculation time is long. This article proposes a three-neighbor search A* algorithm combined with artificial potential fields to optimize the path planning problem of mobile robots. The algorithm integrates and improves the partial artificial potential field and the A* algorithm to address irregular obstacles in the forward direction. The artificial potential field guides the mobile robot to move forward quickly. The A* algorithm of the three-neighbor search method performs accurate obstacle avoidance. The current pose vector of the mobile robot is constructed during obstacle avoidance, the search range is narrowed to less than three neighbors, and repeated searches are avoided. In the matrix laboratory environment, grid maps with different obstacle ratios are compared with the A* algorithm. The experimental results show that the proposed improved algorithm avoids concave obstacle traps and shortens the path length, thus reducing the search time and the number of search nodes. The average path length is shortened by 5.58%, the path search time is shortened by 77.05%, and the number of path nodes is reduced by 88.85%. The experimental results fully show that the improved A* algorithm is effective and feasible and can provide optimal results.

Compliance control is one way to achieve compliance for rigid robots and is widely used in cooperative robots, lightweight robots, and exoskeleton robots. Real-time accurate collection of joint torque data is essential for compliance control during dynamic physical interactions with humans or the environment. Therefore, it is highly desirable to develop high-frequency joint torque sensor (JTS) that are accurate and sensitive and that can be properly calibrated. Toward this end, we propose herein a multi-objective optimization design method to improve the elastic strain distribution in the strain gauge working area, thereby improving the sensitivity of JTS. An analysis and comparison of a variety of easily manufactured inner hole spoke structures shows that the circle-rhombus type spoke structure is the most sensitive. An amplifier and low-pass filter circuit are designed for signal acquisition. An analysis of the sensitivity, linearity, hysteresis, repeatability, resolution, zero drift, and mechanical response of the sensor shows that the optimal sensor designed with high sensitivity of 30.5 mV/Nm, ±100 Nm capacity, 0.1 Nm resolution and 78.8 g weight, and the sampling frequency is 2 kHz. The experimental results show that the JTS is lightweight with high sensitivity and resolution, low noise, high dynamic response, all of which satisfy the design requirements. These results lead to an efficient and economical method of customizing JTS.

Flexible robots with controllable mechanisms have advantages over common tandem robots in vibration magnitude, residual vibration time, working speed, and efficiency. However, abnormal vibration can sometimes occur, affecting their operation. Traditionally only simple mechanisms are considered in studying abnormal vibration, omitting reference to important chaotic phenomena caused by the flexibility of the mechanism rod. In order to better understand the causes of abnormal vibration, our work takes a controllable flexible robot with a complex series-parallel mechanism as a research object and uses a combination of Lagrangian and finite element methods to establish its nonlinear elastic dynamics. The effectiveness of the model is verified by comparing the calculated frequency with the frequency measured in a test. The time-domain diagram, phase diagram, Poincaré map, maximum Lyapunov exponent, and bifurcation diagram of the elastic motion of the robot wrist are studied, and the chaotic phenomena in the system are identified through the phase diagram, Poincaré map, the maximum Lyapunov exponent, and the bifurcation diagram. The relationship between the parameters of the robot motion and the maximum Lyapunov exponent is discussed, including trajectory angular speed and radius. The results show that chaotic behavior exists in the controllable flexible robot and that trajectory angular speed and radius all have an influence on the chaotic motion. Our work provides a theoretical basis for further research on the control and optimal design of flexible robot mechanisms.

The motors and reducers of traditional industrial robots are installed at the joints, which leads to large moment of inertia and difficult to effectively improve the dynamic performance of the robots. In particular, the residual vibration at the end of the robots will significantly reduce its working efficiency and fatigue life. Therefore, this paper proposes a new method to reinstall the motor and reducer near the frame, which can effectively suppress the residual vibration of the robots and simultaneously reduce the moment of inertia. Taking the series industrial robot as the research object, four types of CM robots are designed based on the theory of a multi-DOF controllable mechanism (CM). The motor and reducer of the robot are reinstalled near the frame through different branch chains, and their moments of inertia are calculated and compared. The dynamic equations of residual vibration of the four CM robots considering concentrated mass are established based on the finite element method (FEM) and Timoshenko space beam element (SBE) model, and the correctness of the equations are verified by experiments. The results show that the installation position of motor and reducer has a significant influence on the value of moment of inertia of the robot. The motor and reducer of configuration D are reinstalled near the frame by three branches, which can effectively reduce the attenuation time and amplitude of residual vibration at the end of the robot. The research provides a new idea for improving the dynamic performance of industrial robots.

The current process of vibratory stress relief is limited by centrifugal force produced by eccentric motor since the excitation frequency is mostly less than 200 Hz. The workpiece with high structural stiffness cannot generate enough dynamic stress by the traditional method. In the present work, the vibratory residual stress using pure lateral resonance and the theory of coupled lateral-torsional resonance are compared by the finite element method. Due to the interaction between lateral vibration and torsional vibration, the torsional vibration generated by external lateral excitation can induce coupled lateral-torsional resonance. The large enough dynamic stress is obtained to reduce the residual stress. The principle to reduce residual stress is analyzed by the Unified strength theory. Numeric solutions are obtained to describe the parametric condition to design the device of vibratory stress relief using coupled lateral-torsional resonance. The operating principle of the related device is introduced.